Low Levels of Brain Chemical May Control Appetite

WEDNESDAY, Aug. 27 -- A chemical produced in the brain may play a role in regulating appetite and the likelihood of becoming obese, according to a new study.

For the study, researchers looked at a group of 33 people who had WAGR syndrome, a genetic condition that occurs in one in 500,000 to a million people. WAGR is an acronym for the symptoms that accompany the condition: Wilms' tumor (tumor of the kidneys), aniridia (absence of the iris), genital and urinary tract abnormalties, and mental retardation.

Some people with WAGR syndrome lack a gene for the brain chemical, brain-derived neurotrophic factor (BDNF). Animal studies have suggested that BDNF may help control appetite and weight.

The researchers found that 19 (58 percent) of the 33 study participants had deletions of all or a major proportion of one copy of the gene for BDNF and had correspondingly low blood levels of BDNF.

These 19 participants were all obese by age 10 and had a strong tendency to overeat. The participants who had two working copies of the BDNF gene, on the other hand, were no more likely to develop obesity in childhood than the general population and did not report unusually high levels of overeating.

"This is a promising new lead in the search for biological pathways that contribute to obesity," Dr. Duane Alexander, director of the U.S. National Institute of Health's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), said in an institute press release. "This finding may eventually lead to the development of new drugs to regulate appetite in people who have not had success with other treatments."

The findings are published in the Aug. 28 issue of the New England Journal of Medicine.

According to senior study author Dr. Jack A. Yanovski, of the NICHD's Unit on Growth and Obesity, BDNF is thought to work in combination with a variety of other substances that regulate appetite and body weight, including the appetite-signaling hormone leptin.

Future research looking into the relationship between BDNF and leptin may lead to the development of new therapies for obesity.

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more about obesity.